The present invention relates to the connection of electronic boards in a housing. More particularly, the invention relates to an electronic board carrying connectors to provide a high number of electrical contacts.
As is known, printed circuit boards (PCBs) are a common form of electrical circuit packaging. Today, many electrical systems like computers, routers and switchers are based on a housing containing a backplane circuit board comprising active devices and at least one slot (usually more) to connect an electronic board. Electronic boards are linked to the backplane with connectors, located on the electronic board lower edge and backplane surface, through which signals are transmitted. These connectors are required to some electrical and mechanical requirements: (1) signals must be transmitted efficiently, e.g. without deformation and at high speed; and (2) these connectors must be able to be inserted or extracted easily and must be retained so that electrical connections are not disturbed. Several techniques are known to couple connectors to electronic boards and to backplane boards. Typically, the connector may comprise external pins that go through the board and are welded (soldered) on the other side. The connector may also be soldered on the board surface, e.g. using a known component surface mounting technique, or the connector may be held in place with the use of external and/or flexible pins that go through the board but are not required to be soldered (e.g., on the other side). This last coupling system, referred to as press-fit, is commonly used since it reduces manufacturing cost.
In order to meet miniaturization and increased density design requirements, the electronic packaging industry is requiring a dramatic increase of the number of Input/Output (I/O) contacts (pins and sockets) used in such connecting structures. Progress in the field of the Information Technology (IT) equipment has resulted in electronic boards with improved impedance, better dielectric (e.g., PTFE) insulators, and improved mechanical strength and geometry. However, meeting such requirements are making the mechanical packaging of these structures more costly from both a development and manufacturing standpoint. Additionally, such relatively complex structures make the installation and the removal of logic boards from the backplane a sometimes difficult job. Still further, as the number of electrical contacts increases, the force required to insert or extract an electronic board from a housing understandably increases correspondingly.
FIG. 1, showing a conventional backplane 100 equipped with a first connector 110 and a larger, second connector 115 mounted on an electronic board (printed circuit board, or PCB) 105, illustrates the force 120 exerted to insert or extract PCB 105. This force is not applied directly on the connector for practical reason, e.g., the connector 115 is carried both on the lower edge of the electronic board, and also on the face thereof. Consequently, because of the connector width and the mechanical resistance of the electrical contacts, force 120 produces vertical force 125, rotational force 130 and lateral force 135 that help separate connector 115 and electronic board 105 from the backplane. Furthermore, these forces, asymmetrically distributed upon PCB 105, may cause damage to the electronic board or the electronic devices (not shown) positioned on its surfaces. To remove this risk, the separation force must be applied symmetrically on PCB 105 and also on the electrical contacts positioned on the side of the PCB adjacent its soldered lower edge. Obviously, connectors with pins that go through the PCB, e.g., soldered pin or press-fit connector, cannot be used since this may result in electrical shorts between connectors.
FIG. 2 illustrates a known way to use symmetrical surface mounted connectors. This coupling system distributes the force on two connectors 115xe2x80x2-1 and 115xe2x80x2-2 to thus reduce the risk of damaging the PCB 105 and/or the devices mounted on its surfaces. Likewise, in comparison to FIG. 1, the smaller width of each of this pair of connectors reduces the risk of undesirable separation of connectors 115xe2x80x2-1/115xe2x80x2-2 from PCB 105. Nevertheless, while this FIG. 2 connecting system substantially prevents damaging the PCB and/or its positioned components, the use of connecting solders increases the chances for separation at these solders, which solders may break due to excessive shearing forces. As seen, connectors 115xe2x80x2-1 and 115xe2x80x2-2 do not include pins as does connector 115, to strongly hold both connectors to place during force application.
It is believed, therefore, that an electronic board assembly which overcomes the disadvantages of the aforementioned conventional assemblies would constitute a significant advancement in the art.
It is an object of the invention to enhance the electronic board assembly art.
It is another object of the invention to provide an electronic board assembly which carries connectors on each side thereof that can withstand the relatively strong forces required to insert or extract a board.
It is a further object of the invention to provide such an assembly which can be produced in a relatively facile manner, thereby keeping the costs associated with such assemblies relatively low.
The accomplishment of these and other related objects is achieved by an electronic board assembly that comprises two elementary electronic boards, coupled together, each of said two elementary electronic boards carrying at least one connector on its external lower edge. At least one of these connector comprises external pins that go through the elementary electronic board carrying said at least one connector.
Further advantages of the present invention will become apparent to one skilled in the art upon examination of the drawings and detailed description provided herein.